Phonograph pickup having permanent magnet armature



H. A. GREENER May 16, 1950 PHONOGRAPH PICKUP HAVING PERMANENT MAGNET ARMATURE Filed Dec. 22. 1945 4 Sheetsfiheet l INVENTOR. HAZE) A, 6ZEE VEE May 16; 1950 H. A. GREENER PHONOGRAPH PICKUP HAVING PERMANENT MAGNET ARMATURE Filed Dec. 22, 1945 4 Sheets-Sheet 2 INVENTOR. HAZZV A. @ZEENEZ May 16, 1950 H. A. GREENER 'PHONOGRAPH PICKUP HAVING PERMANENT MAGNET ARMATURE 4 Sheets-Sheet 3 Filed Dec. 22. 1945 R m w mm M WW W V. E M L H 17 W 11% E A Hm 1w y 6, 1950 H. A. GREENER 2,507,708

PHONOGRAPH PICKUP HAVING PERMANENT MAGNET ARMATURE Filed Dec. 22, 1945 4 Sheets-Sheet 4 INVENTOR. Hazzx ,4. 6ZEENEZ BY p Patented May 16, 1950 UNITED STATES PATENT OFFICE PHONOGRAPH PICKUP HAVING PERMA- NENT MAGNET ARMATURE Harry A. Greener, Trucksville, Pa, assignor to Pennsylvania Electronics Incorporated, Philadelphia, la., a corporation of Pennsylvania Application December 22, 1945, Serial No. 636,706

2 Claims.

This invention relates to devices for converting energy and particularly mechanical energy into electrical energy, or electrical into mechanical energy, and in particular, relates to a pick-up for phonograpns and the like, where the indentations of a sound track are converted into acoustic impulses.

The pick-up of this invention has high output and is of the velocity type, requiring the least to electrical or electrical to mechanical.

The purpose of this invention is to provide means for readily converting mechanical energy, such as variations in the track of a phonograph record, into electrical energy, for acoustic reproduction, which is relatively small and compact,

which may be reversed to convert electric energy into mechanical energy, such as impressing sound tracks on phonograph records and the like.

One of the objections to pick-up systems of this type is the hum resulting from lines of force from an outside source and particularly coming at any angle in relation to the axis of the pick-up and this invention, therefore, involves a core type 'constrifiction which is particularly adapted for hum bucking purposes.

Phonograph records are formed with the variations in the spiral tracks either vertically or laterally positioned as in wavy tracks, and therefore in a pick-up for this purpose it is required that the pick-up agent rotate about either a horizontal or perpendicular axis.

The invention particularly relates to a stylus or needle mounted in a permanent magnet positioned between the poles of a soft iron core having coils around the sides thereof in which the needle rotatively vibrates the magnet causing variations in the magnetic flux whereby impulses are transmitted through coils around the sides of the soft iron core.

The object of this invention, therefore, is to provide means for vibrating a permanent magnet between poles of a soft iron core wherein the paths of magnetic flux between the opposite poles of the magnet and the adjacent poles of the core are intensified and relieved to influence circuits in coils around the core accordingly.

With these ends in view, the invention embodies a permanent magnet on a rotatable arma ture in which the magnet is positioned between the poles of a laminated soft iron core having transmitting coils therearound and means is provided for positioning the magnet between the poles and for mechanically rotating the armature.

For a full and more complete understanding of the invention, reference may be had to the following description and accompanying drawings, wherein:

Figure 1 illustrates the application of the pickup in a housing of a convenient design.

Figure 2 is a similar view with the housing and pole pieces of the core separated from the base to show the relative positions of the parts.

Figure 3 is a detail showing the armature.

Figure 4 illustrates the core, magnet, and stylus of the pick-up with the supporting parts of the magnet indicated in dotted lines and with the magnet positioned in the gap for rotation about a horizontal axis.

Figure 5 is a similar view with the magnet positioned for rotation about a vertical axis.

Figure 6 is also a similar view showing the magnet in a different position and with a stylus of a different type mounted therein.

Figure 7 is also a similar view showing a U shaped magnet in the core gap.

Figure 8 also shows a similar view with a magnet of the induced pole type incorporated therein.

Figure 9 is a detail illustrating the magnet shown in Figure 8.

Figure 10 illustrates a typical mounting of the magnet in the gap of the core, with the magnet rotated slightly.

Referring now to the drawings wherein like reference characters denote corresponding parts, the magnet is indicated by the numeral ID, the soft iron core by the numeral ll and the stylus by the numeral 12.

In the design shown in Figure 4, a magnet 10 is positioned in the gap of the core with the north poles at the top and the south poles at the bottom and, normally, the lines of flux through the poles will travel in oppositely moving circles 13 and M with the flux of the core ll traveling around as indicated by the line l5. When the point of the 3 needle moves to the right so that the needle is rotating in a counter-clockwise direction, the flux will rotate through the core in the direction of the arrows l6, and when the needle moves to the left or rotates the magnet in a clockwise direction, the flux will rotate through the core in the direction of the arrows IT.

The magnet H) which is positioned in the gap in the core may be mounted through bearings as shown in Figure 2, or may be held by blocks of rubber or other resilient material, as shown in Figure 10, with the blocks positioned in recesses in the pole pieces and magnet, or it may be held by resilient elements 5 as indicated in Figure 4, or by any suitable means.

Coils l8 and is are wound around the sides of the core H and these may be connected through leads 2% and 21, either in series or parallel to acoustic reproducing means, and the magnetic flux travelling first in one direction and then in the other, will influence the coils for the transmission of impulses thereof to acoustic reproducing means.

. vThe direction of the flux in the core results from the relative positions of the poles of the magnet as when the point of the needle moves toward the right the upper north pole and lower south pole will move toward their respective ends of the core, as shown in Figure 10, substantially closing the gaps therebetween, thereby facilitatin'g travel of the magnetic fiux between these poles and at the same time restricting the travel of the flux between the poles at the opposite coropening in the cover the poles may be set against the shims and secured by the screws in'the cover thereby insuring accurate and equalized gaps between the poles and magnet. In this design, the core is formed of L-shaped laminated pieces 36 and 31 with their outer ends in abutting relation and with their inner ends positioned to engage corresponding surfaces of the poles 32 and 33 when the poles are in their respective positions in the slots 34 and 35. Coils or windings 38 and 39, corresponding to the coils I8 and [9, are formed around the sides of the core as shown. The coils may be connected in series or parallel as may be desired and leads 4B and ll may extend therefrom to converter or amplifying tubes as may be desired. The unit may be provided with a cover 2 -iat may be held to the base by screws 43 or any suitable means. The design and arrangement of the base and cover or any of the mounting parts may be changed to correspond to the particular application of the pickup in a machine or device as desired.

In the design shown in Figure 5, the magnet is shown with the north and south poles, and also the core and winding, substantially the same as shown in Figure 4. However, the stylus as indicated by the numeral 44 extends straight downward and, with the magnet rotatable on a horizontal axis, the stylus will move the respective ners, causing the flow of the flux in the direction A of the arrows l6 as described. When the needle moves toward the left or in the opposite direction, the upper right hand north pole will move toward the corresponding pole of the core and the lower left hand south pole will also move towardthe lower part of the pole of its corresponding pole of the core, thereby facilitating travel of the flux between these poles and restricting travel between the opposite poles so that the flux will travel in the direction of the arrows I as described.

This description of the alternating directions of travel of the magnetic flux through the laminated soft iron core I! is characteristic of the travel of the flux in the following alternate designs and arrangements, using the difierent designs of magnets.

The magnet, stylus, and coil herein described may be used in housings of various designs and various means may be provided for mounting or installing the various parts therein. A typical application and installation of the pick-up is illustrated in Figures 1, 2 and 3, in which a stylus 22 is attached to a magnet 23 through an armature 24, and the armature is rotatably mounted in V-shaped bearings 25 and 26 in a base 21 through bushings 28,and 29 of rubber or other resilient material. The bushings provide clamping means, which with the stylus extending through an opening 30, provide a floating mounting so that the armature is free to vibrate or rotate slightly in the yielding bushings. The magnet 23 being mounted on a tongue 3| of the armature is suspended between pole pieces 32 and 33 adapted to be positioned in slots 34 and 35 with their inner surfaces slightly spaced from the edges of the magnet. The pole pieces 32 and 33 are shown removed from their positions in the slots and in use they are inserted with the armature and cover in place. By inserting shims against the sides of the magnet through the poles with substantially the same movements as illustrated and described in the design shown in Figure 4 and the flux will travel through the core in a similar manner.

In the design shown in Figure 6, the core H and coils iii and 19 are similar to those illustrated in Figure 4. However, the magnet is positioned for vertical rotation with the north poles 4-5 at the front and the south poles 48 on the inside. The stylus 41 extends downward from the lower side of the magnet and outward, and the needle point thereof is mounted to rotate the magnet about a vertical axis whereby one of the north poles and the diagonally opposite south pole will approach their respective poles of the core I I when the magnet is rotated in one direction, and the other north pole and the diagonally opposite south pole will approach the poles of the core when the magnet is rotated in the opposite direction. The lines of flux traveling through the poles substantially in contact will travel first in one direction and then in the other.

A magnet of a diilerent type is illustrated in Figure '7, in which the north and south poles thereof are connected by a member at one side only instead of in the center, thereby forming a U-shaped magnet. However, one leg 48 thereof will constitute the north pole and the other leg 49 the south pole, and with the stylus 50 mounted to rotate the magnet about a horizontal axis, the north pole at one edge of the magnet and the south pole at the diagonally opposite edge will approach their respective poles of the core with a movement corresponding to that described and illustrated in Figure 4. The lines of flux in the core will also travel in opposite directions in the same manner.

In the pick-up illustrated in Figures 8 and 9, which is of the induced pole type, the flux can be increased without increasing the mass of the moving systems. This is formed with soft steel blocks 5! and 52 interposed between the gap faces 53 and 54 in place of the vibrating magnet, and the output can be increased to any desirable value consistent with the other parameters. In this design the areas in the gap are exaggerated for the purpose of illustration, and it will be understood that the gap surfaces should be as close as possible without touching for maximum output. In this design the poles 55 and 56 of the magnet 51 are positioned so that as the stylus bar 58 rotates on a horizontal axis the north pole edges at one side of the magnet will approach and at the same time the diagonally opposite edges of the south poles will also approach, thereby facilitating travel of the lines of fiux through these points, and then as the stylus rotates in the opposite direction so that the opposite poles will approach the lines of flux will travel through the opposite points wherein the flux will travel first in one direction in the core and then in the opposite direction as illustrated and described in Figure 4.

Figure illustrates a suggestive mounting for a permanent magnet in the gap between the poles of a core, and in this design the magnet 59 is formed with grooves 60 and 61 in the edges, and corresponding grooves 62 and 63 are provided in the poles 64 and 65 of the core. The magnet is suspended and centered in the gap by rubber cylinders 66 and 61 having fins 68 and 69, and I0 and 'Hwhich provide separators between the poles. When the magnet is influenced in one direction, as shown, the elastic fins 6B and II will be squeezed until they barely separate the 1,.

pole pieces, whereas the fins 69 and H1 will expand, and then as the magnet rotates in the opposite direction, the fins 69 and 10 will be fiattened and the fins 68 and H will expand. Then when the magnet is released it will be centered in the gap by the elastic fins.

This oscillating movement of the magnet causes fluctuations in the magnetic flux, and these are transmitted by the coils. In the same manner the magnet may be vibrated by fluctuating impulses imparted through the coils and core thereto, and the magnet will vibrate the stylus or needle to produce corresponding fluctuations in the sound track being contacted by the said needle.

The poles at the ends of the core ll directly associated with the poles of the magnet may be formed with continuous surfaces, as shown in Figures 4, 6, and '7, or these surfaces may be separated with gaps 66 and 61, as illustrated in Figure 10, thereby defining poles corresponding to adjacent poles of the vibrating magnet. These gaps or Open spaces may be formed as illustrated in Figure 10 or as shown in Figure 2 in which they are indicated by the numerals l2 and '13, or may be elongated as illustrated in Figure 5 in which they are indicated by the numerals 14 and These open spaces between the respective ,pdles prevent bleeding the magnet and also provide means whereby the magnet may be reenergized without being removed from the trans- .6 ducer. The longer the slot or open space between the poles, the longer the path of the magnetic flux and the higher the reluctance. These open spaces provide less shunting effect on the magnet and thereby increase the flux diiferential.

It will, therefore, be understood that magnets of various designs and shapes, and comprising various parts may be used and interposed between the poles or in the gap of the core and these may be vibrated in diiferent planes, and as any of the various designs are electromechanically reversible, they may be used in any of the various electromechanical transducers.

While a preferred specific embodiment of the invention is hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact construction illustrated and described because various modifications of these details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In an electromechanical transducer, the combination of z a core in the form of a loop having a gap therein, a pair of coils carried by said core on opposite sides of said gap, a permanent magnet having opposed poles, means for mounting said magnet in said gap for movement therein with said poles lying completely within said gap, and a stylus carried by said magnet.

2. In an electromechanical transducer, the combination of: a core or rectangular formation having side and end pieces, one of said end pieces having a gap therein, a coil on each of said side pieces, a permanent magnet having opposed poles separated -by recesses in opposite faces of said magnet, means for mounting said magnet in said gap for movement therein with said .poles lying completely within said gap, a stylus, and mechanical connections between said stylus and said magnet.

HARRY A. GREENER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,728,278 Miessner Sept. 17, 1929 1,834,359 Vansickle Dec. 1, 1931 1,916,703 White et a1. July 4, 1933 1,967,335 Steigman July 24, 1934 2,073,561 McCracken Mar. 9, 1937 2,110,153 Holst Mar. 8, 1938 2,212,530 Weil Aug. 27, 1940 FOREIGN PATENTS Number Country Date 336,648 Great Britain Oct. 15, 1930 716,223 France Oct. 6, 1931 

